EE WAS STACKING 100# SACKS OF PRODUCT ONTO PALLETS. AFTER FINISHING A SERIES, THE CREW TOOK A 10 MINUTE BREAK, AT WHICH TIME THE EE STARTED FEELING TIGHTNESS IN HIS LOWER BACK ON THE RT SIDE A BOVE HIS HIP. HE FINISHED HIS SHIFT, SYMPTOMS WORSENED BY MORNING, SO HE THEN SOUGHT MEDICAL TREATMENT THE FOLLOWING DAY--3/8/02.